1. Field of the Invention
The present disclosure relates to swirlers, and more particularly to air swirlers such as used in pure airblast fuel injectors for gas turbine engines.
2. Description of Related Art
A variety of devices and methods are known in the art for injecting fuel into gas turbine engines. Of such devices, many are directed to injecting fuel into combustors of gas turbine engines under high temperature conditions.
In a fuel injector for a gas turbine engine, inner air swirlers are used to impart a tangential velocity component to the air, setting up a radial pressure gradient that biases the highest velocity air towards the outer diameter of the air passage where the air meets up with the fuel. This higher velocity improves atomization of the fuel. In addition to the inner air swirlers, outer air swirlers are also present which, along with the inner air circuit, help to distribute the fuel into the combustor.
Air swirlers are subjected to hot air from the compressor, which can be at temperatures as high as 1300° F. (704° C.), and these temperatures will rise as the demand for higher compression ratios continues. Yet there are other areas of the injector in direct contact with fuel, which tends to remains much cooler than the compressor discharge air. As a consequence, the vanes in injector air swirlers act like heat exchanging fins. Due to their relatively small mass and heat fin behavior, these air swirlers tend to heat up faster than their surrounding structure. This is especially the case for transient events. Another driving mechanism for thermal stress in the outer air swirler is radiation from the flame front within the combustor. As design requirements drive toward ever hotter compressor discharge temperatures, compressor discharge air is becoming less effective at cooling outer air swirler surfaces that heat up due to flame radiation.
As current and future engines continue to increase in operating pressure ratio, the temperatures exiting from the compressor are expected to climb, while fuel temperatures are expected to remain below carbon formation temperatures. Therefore, the temperature differential to which future fuel injectors are expected to be subjected is expected to grow, leading to higher stresses and presenting limitations on the life of the injector.
Such conventional methods and systems have generally been considered satisfactory for their intended purpose. However, there is still a need in the art for improved swirlers and injectors. The present disclosure provides a solution for this need.